“As you move forward [in time], the information degrades,” said Mearns. “The information today is worse than yesterday, and tomorrow will be worse than today.”

But the hard truth is that the families of the passengers and crew of Malaysia Airlines Flight 370 (MH370) may only find closure when they see significant portions of the aircraft’s mainframe being winched to the surface.

Even so, the challenges facing the search effort continue to mount. In addition to fighting the vagaries of a largely undefined search grid; searchers are increasingly at the mercy of deteriorating weather as the region now heads into Autumn.

Bathymetric map of the Indian Ocean (Photo credit: Wikipedia)

Some have compared the current search and recovery effort with similar efforts after the 2009 disappearance of Air France Flight 447, in which an Airbus A330 aircraft went missing in the Atlantic while en route from Rio de Janeiro to Paris. But Mearns says the area now being searched for MH370 is even more remote.

With the MH370 search, the weather is the biggest complication, says Mearns, who notes that the current southern search area generally has inclement weather, whereas the Air France search region generally had what he termed “benign” weather.

As Mearns acknowledges, however, some totally unexpected new lead could still totally change the odds. And if so, then the long search for the 777 would become a retrieval operation.

One such scenario involves getting extremely lucky in detecting acoustic pings from the aircraft’s flight data and cockpit voice recorders, or the aircraft’s two “black boxes” which hold the ultimate clues in unraveling the mystery behind the plane’s disappearance.

But as Mearns points out, acoustic pingers attached to the black boxes only have a nominal life of 30 days, more than half of which has already been spent. And he’s not optimistic that the search team will have what he terms a "defined search box" in which to deploy acoustic sonars to listen for the data recorders.

“It’s a one-in-a-million chance that the searchers will be able to hear those pingers,” said Mearns.

If the wreckage is found, however, Mearns has a high degree of confidence that the black boxes will be in the same underwater debris field. Searchers would likely use a remotely-operated underwater vehicle (ROV) with a video-equipped system and robotic arms to look search for and retrieve the black boxes.

“The data recorders can resist very high pressures, so the information should survive,” said Andreas Villwock, a meteorologist at GEOMAR, part of Germany’s Helmotz Center for Ocean Research.

But to find the wreckage without lucking up on the pinging black boxes would, says Mearns, require deploying towed side-scan sonars from the surface into very deep water, some 300 meters (984 ft.) above the ocean floor.

“The Air France flight was 3900 meters (12,792 ft.) deep and nominally this area is more or less the same,” said Mearns. “But the search area with the Air France flight was able to be refined to a very small area; that’s not the case with MH370.”

At roughly 45 degrees South latitude south and 90 degrees East longitude, Villwock says the MH370 search area is one in which the ocean-floor topography seems to be relatively flat; which, he says would make a detailed underwater search and retrieval mission a bit easier.

“We think the area is more like a deep basin abyssal plain,” said Villwock. “But the undersea maps that we have are not very good in the southern Indian Ocean.”

Even so, Villwock says programmed autonomous underwater vehicles (AUVs) which are set on predetermined courses could find it.

Villwock sees the search and recovery as two separate missions; first of finding a significant portion of the aircraft on the seafloor itself and then the arduous operation of actually recovering what remains of its structure.

ROVs can use video-controlled "grabs" that can pick up smaller pieces of the aircraft, says Villwock. But, he notes that to retrieve a large portion of the fuselage itself would likely require that the wreckage be put on undersea platforms that, in turn, could be raised to the surface.

“Even though these deepwater operations are very complex; if they find the wreckage, they can recover it,” said Mearns. “The real challenge on this one is finding it.”